The forming of the tension of optical fibre and controlling it even in demanding production situations is essential in the production of a conductor element containing optical fibres, in the production of parts for a loose protective structure, for example, whether a so-called minitube or a so-called minitube ribbon or maxitube is being produced. A minitube refers to an element part of a multi-element stranded cable and a maxitube refers to a basic element of a single-element optical cable.
The requirements for a loose protective structure of the conductor element have changed recently and emphasis has been laid on both structure and production requirements. The filling gel is required to have a greater viscosity than before and thixotropy is required for tropical conditions, for example. The costs will raise production and structural requirements. This has caused technical problems to the realization of prior art solutions.
The solution disclosed in Finnish Patent Specification 85,310 can be mentioned as an example of prior art solutions. This solution is quite satisfactory for some situations, but a drawback is that the solution is only suitable for levelling out differences in fibre lengths. Tension differences of fibres cannot be levelled out with the solution.
German Offenlegungsschrift 41 14 299 can be mentioned as a second example of prior art solutions. A disadvantage of this solution is that it uses specific controlled starting reels, which makes it rather complicated to accomplish it in practice.